1. Field of the Invention
The present invention is directed to nuclear magnetic resonance devices, and methods for operating such devices, for identifying nuclear magnetic spectra from spatially selectable regions of an examination subject.
2. Description of the Prior Art
Nuclear magnetic resonance devices are generally known in which an examination subject is placed within a fundamental field, generated by fundamental field coils, and in one or more gradient fields respectively generated by gradient coils. An RF transmitter supplies a sequence of RF pulses to the patient via an antenna, and an RF receiver receives the resulting nuclear magnetic resonances signals from the patient, and supplies these signals to a computer for evaluation. A slice of the examination subject can thereby be selectively excited to generate nuclear magnetic resonance signals by applying a gradient field together with a frequency-selective RF pulse. In nuclear magnetic spectroscopy, limitation of the examination to selected volume regions, for example, a particular organ, is generally desired. In a known method described in the article "Depth-Resolved Surface-Coil Spectroscopy (DRESS) For In Vivo .sup.1 H, .sup.31 P, and .sup.13 C NMR," Bottomley et al, Journal of Magnetic Resonance, Vol. 59 (1984) pages 338-342, a slice of the examination subject is excited for this purpose by applying a gradient field together with a frequency-selective excitation pulse. Only a one-dimensional topical resolution is possible using this method. A further selection can be undertaken by using surface coils which again select a portion of the first-selected slice in accord with their sensitivity range.